The wife of jailed former Pakistani Prime Minister Nawaz Sharif has died at a clinic in London after battling cancer for more than a year, her family said. She was 68.

'My sister-in-law and wife of Mian Nawaz Sharif is no more among us,' Sharif's younger brother and head of his Pakistan Muslim League Nawaz (PML-N), Shahbaz Sharif, said on his party's official Twitter account.

Kulsoom Nawaz was put on a ventilator a day earlier after her condition worsened, the family said. She was diagnosed with lymphoma in August 2017 and had been receiving treatment at a private hospital in London for several months.

Sharif, a three-time prime minister, is serving a 10-year prison term in Pakistan following his conviction on corruption charges in early July. The couple's daughter Maryam Nawaz is also in prison.

Nawaz Sharif and his family contend that the cases, convictions, and sentences against them are politically motivated.

Prominent Pakistani television anchor Syed Taliban Hussain tweeted a video showing Sharif taking care of his ailing wife in Britain hours before he and his daughter returned to Pakistan following their convictions.

Kulsoom Nawaz had been at her husband's side throughout his decades-long political career.

New Prime Minister Imran Khan, a former cricket star who campaigned against the Sharifs, sent his condolences.

'Mrs. Kulsoom Nawaz was a brave woman,' Khan's office said in a statement.

Other Pakistani political leaders and civil-society representatives also expressed grief over her death.

With reporting by dpa, Reuters, and AFP RFE/RL's Radio Mashaal

Radio Mashaal was launched in January 2010 in order to counter a growing number of Islamic extremist radio stations in Pakistan's Northwest Frontier Province (now Khyber-Pakhtunkhwa Province) and the Federally Administered Tribal Areas along the border with Afghanistan.